MD59-0062 M/A-COM, Inc., MD59-0062 Datasheet - Page 4

• Manufacturer Part Number: MD59-0062
• Description: PCS Cdma Upconverter/driver 1710-1910 MHZ
• Manufacturer: M/A-COM, Inc.

Specifications subject to change without notice.
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Visit www.macom.com for additional data sheets and product information.
PCS CDMA Upconverter/Driver, 1710-1910 MHz
North America: Tel. [phone], Fax [phone]
Asia/Pacific: Tel.[phone], Fax [phone]
Europe: Tel. [phone], Fax[phone]
Operating Instructions
The MD59-0062 is a highly integrated MMIC upcon-
verter / driver for the 1710 - 1910 MHz PCS band. The
upconverter / driver provides exceptional RF perform-
ance while consuming low DC current and is packaged
in a low cost plastic package. It is ideal for lightweight
battery operated portable radio systems.
The transmit chain consists of a balanced IF amplifier,
balanced mixer with single-ended RF output, and a two
stage RF driver amplifier as shown in the block dia-
gram. The user must add surface mount resistors, induc-
tors and capacitors in conjunction with the IC to opti-
mize the trade-offs among performance, tunability and
ease of use. A schematic on page 4 shows the IC and
required off-chip components.
An off-chip self-bias resistor R1 with an RF bypass ca-
pacitor allows the current in the driver amplifier to be
varied to obtain the required linear output power. By
placing a bipolar transistor in series with the self-bias
resistor, you can dynamically switch the current draw in
the driver to provide high and low power operating
modes. In high power mode, the bipolar transistor is on
and the driver output stage is self-biased through R1 to
provide +7 dBm of linear output power. By switching
off the bipolar transistor, the output stage is biased
through the higher resistance R2 thus reducing the cur-
rent by ~25 mA to give 0 dBm of linear output power.
An external filter is required between the mixer output
and driver amplifier input to reduce the amplitude of the
image and local oscillator signals coming out of the
mixer. This filter should have a 50
impedance.
The mixer is a balanced resistive FET mixer that pro-
vides exceptional linearity and isolation with low loss
and no DC current.
The IFA input ports are externally matched to 265 ohm
differential impedance using two off-chip capacitors and
an off chip inductor. This allows maximum flexibility
of intermediate frequency and IF filter. The IFA output
ports are matched to the mixer using off chip inductors,
which are also used for DC bias injection. A matching
network such as that shown below can be used to match
both the input and output of the IFA at the required fre-
quency. The inductor also acts as a choke for the DC
supply line.
input and output
The LO input port is matched on-chip to 50 ohms. An
LO buffer amplifier boosts the -10 dBm input signal to
the level required to drive the mixer. The converter
reaches optimum performance with a drive level of -5
dBm.
All DC supply lines must be properly bypassed at RF
frequencies to obtain optimum performance and at
lower frequency to maintain unconditional stability.
Capacitors C1, C3, C8 are RF bypass capacitors for the
LO amplifier and the driver amplifier. The value and
placement of these capacitors is critical in determining
the frequency response of these amplifiers. Capacitor
C10 is a source bypass capacitor for the second stage of
the driver amplifier. The placement of this capacitor
will affect the gain of the amplifier. For best perform-
ance, place all the RF bypass capacitors as shown in the
PCB drawing on the previous page. Capacitors C2, C4,
C5 and C9 are 1000 pF low frequency DC supply by-
pass capacitors. Their values and placement are less
critical than the other capacitors. However, for best
results, place thes e capacitor as close to the package
leads as possible.
MD59-0062
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